EVOLUTION OF MITOCHONDRIAL-DNA SEQUENCES IN XENOPUS
EVOLUTION OF MITOCHONDRIAL-DNA SEQUENCES IN XENOPUS
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DOI：
10.1016/0012-1606(72)90051-6
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发表时间：
1972-01-01
影响因子：
2.7
通讯作者：
DAWID, IB
中科院分区：
文献类型：
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作者：
DAWID, IB
非洲爪蟾和非洲爪蟾是两种有亲缘关系的两栖动物，它们可以杂交产生能存活的杂交后代。它们的线粒体DNA（mtDNA）1的大小，组成和序列进行了比较。两者均为环状分子，分子量为11.5 ~ 11.7 × 106道尔顿。它们在氯化铯中的密度和在两种溶剂中的热变性曲线是不可区分的;从这些值中，它们的核苷酸组成已被计算为41%GC。大、小线粒体rRNA由X.莱维斯和X. mulleri的线粒体DNA的核苷酸序列在X. Laevis不同于X中的那些。mulleri两个物种的mtDNA的分离链在所有可能的组合中重新退火，并分析产物的热稳定性。结果表明：（1）X.莱维斯和X. mullerido不相互作用，表明这些区域中大约一半的碱基不同;（ii）大约50%的mtDNA形成异源双链体，平均27%的碱基错配;（iii）20%的mtDNA形成异源双链体，平均6%的mtDNA形成异源双链体。线粒体DNA与不同RNA的杂交表明，线粒体rRNA和4S RNA的编码序列在不同的基因组中更为相似。两个异种物种的DNA序列。这些表达的rRNA和4S RNA区域占线粒体DNA的20%，其序列在进化过程中分化最小。这表明，剩余的，快速进化的mtDNA序列可能相当于“间隔”序列已被发现在某些核DNA。
Xenopus laevisandXenopus mulleriare related amphibian species which can be crossed to give viable hybrid progeny. Their mitochondrial DNAs (mtDNAs)1have been compared with respect to size, composition, and sequence. Both are circular molecules with a molecular weight of 11.5 to 11.7 × 106daltons. Their densities in CsCl and thermal denaturation profiles in two solvents are indistinguishable; from these values their nucleotide composition has been calculated to be 41% GC. The large and small mitochondrial rRNA encoded by the mtDNA ofX. laevisandX. mullerihave the same or a very similar size.The nucleotide sequences of mtDNA inX. laevisdiffer from those inX. mulleri. Separated strands of mtDNA of both species were reannealed in all possible combinations, and the thermal stability of the products analyzed. This experiment led to the conclusion that (i) about 30% of the sequences in mtDNA ofX. laevisandX. mullerido not interact, indicating that about half of all bases in these regions differ; (ii) about 50% of the mtDNAs form a heteroduplex with an average of 27% mismatched bases; (iii) 20% of the mtDNAs form a heteroduplex with an average of 6% mismatched bases.Hybridization of mtDNA with different RNAs showed that the sequences coding for mitochondrial rRNA and 4 S RNA are more similar in the twoXenopusspecies than the other sequences in the DNA. These expressed rRNA and 4 S RNA regions account for the 20% of mtDNA whose sequences have diverged least during evolution. It is suggested that the remaining, rapidly evolving sequences of mtDNA may be equivalent to the “spacer” sequences which have been found within certain nuclear DNAs.